Mr. Trump is expected to make the formal declaration and deliver a major speech on the topic Thursday, more than two months after he first announced that would be his plan.

Mr. Trump said last week that creating a national emergency is “time-consuming work,” but he promised an announcement is coming. White House spokeswoman Sarah Huckabee Sanders went further, saying “there’s a very in-depth legal process that goes with declaring a national emergency.”

In addition, Mr. Trump’s nominee for drug czar, Rep. Tom Marino, withdrew his name from consideration for the post after a bombshell report by “60 Minutes” and The Washington Post.

Sunday’s in-depth story spotlighted former DEA deputy Joe Rannazzisi’s details on how thousands of opioids were pumped into American communities through pharmacies — and thousands became addicted and died.

“This is an industry that’s out of control,” Rannazzisi said. “What they wanna do, is do what they wanna do, and not worry about what the law is. And if they don’t follow the law in drug supply, people die. That’s just it. People die.”

There is concern the White House actions will be empty talk without a long-term commitment to paying for more addiction treatment: An emergency declaration would lack punch without money, said Andrew Kessler, who represents substance abuse treatment providers as a lobbyist in Washington.

“If there’s no new money to expand our treatment infrastructure, I don’t know what the punch is going to be,” Kessler said. He acknowledged that declaring a national emergency “would put it in the national spotlight. Create buzz. Create talk.” But with news coverage of the opioid crisis already saturating front pages and newscasts, he said, “I don’t know how much more buzz we can generate.”

Some health advocates also worry that devoting more public health resources to opioids could pull attention and resources from other health problems such as cancer, diabetes and heart disease. What’s needed, they say, are new funding streams and a willingness to work hand-in-hand with states and local governments.

“An emergency declaration without significant new funds will likely be unsuccessful. The problem is enormous and requires a similar investment in a comprehensive strategy that includes primary prevention,” said Becky Salay, director of government relations at Trust for America’s Health, a Washington-based public health research and advocacy organization.

The idea of declaring a national emergency was first raised in an interim report prepared by an opioid commission chaired by New Jersey Gov. Chris Christie and convened by the president earlier this year.

“The first and most urgent recommendation of this commission is direct and completely within your control. Declare a national emergency,” read the report from the group, which argued the move would empower Mr. Trump’s Cabinet to address the crisis and force Congress to dedicate more money to fighting overdose deaths.

Mr. Trump said back in August he planned to adopt the recommendation, and claimed his team was working on documents to formalize the declaration. But his words spurred immediate push-back from some inside his administration who argued it wasn’t the best move.

Emergency declarations are typically reserved for natural disaster like hurricanes, infectious diseases like swine flu and bioterrorist threats like anthrax, and Trump’s now-departed Health and Human Services Secretary Tom Price argued publicly that the administration could deploy the needed resources without a formal declaration.

As the weeks have passed, Christie appeared to grow impatient, telling an audience in New Jersey earlier this month that it wasn’t “good that it hasn’t been done yet.”

“All I know is, two months is two months and I would have loved to have had the time to have worked on it in that respect,” Christie said. “But you know, they’re telling me they’ve got legal issues and hurdles to get over that they haven’t gotten over yet. I take them at their word. But if you’re asking me, would I have preferred him to sign it August 1st, yeah.”

He said the problem was too big to say the delay had made a significant difference, “but I would also say you can’t get those two months back.”

The Office of National Drug Control Policy defended the administration’s handling of the matter, saying Trump’s policy advisers, along with relevant government agencies, have been “working tirelessly since the beginning” to respond to the opioid crisis.

With an estimated 142 Americans dying every day from drug overdoses, more than 10,000 people have died in the weeks since the president first committed to the plan.

At a commission meeting last week, no overt reference was made to the president’s promise, but members stressed the need to act.

“We ought to be treating this like a FEMA response and getting the necessary medication,” said former Rep. Patrick Kennedy, who argued that, if the drug crisis were Ebola, “we’d waive all the rules and we’d say get it done and start saving lives, I mean that’s what we need.”

“That’s what we’ve been saying,” Christie responded. The New Jersey governor later compared the response to the AIDs epidemic.

“I still have not seen the passion for this epidemic that I saw in the AIDS epidemic,” Christie said.

The commission had suggested two mechanisms for an emergency declaration: the Public Health Service Act or the Stafford Act. The nation has a public health emergency fund, but it is empty, Kessler said.

If the emergency is declared instead under the Stafford Act, funding could be included with disaster relief for hurricanes and wildfires. But that would put the opioids emergency under the jurisdiction of the Federal Emergency Management Agency, which is under the Department of Homeland Security.

“All that money could go to border security and drug interdiction, rather than toward treatment,” Kessler said.

Mr. Trump’s delays have frustrated observers.

“The failure to follow through is a betrayal of families and I think unconscionable,” said Lawrence Gostin, a Georgetown University professor and the director of the World Health Organization Collaborating Center on National & Global Health Law.